Kind of a shower thought, and maybe it’s just how I run campaigns, but it feels like there’s a lot of parallels between DMing and that guy who has a great idea for a book/movie but will never write a single page.
The DM comes up with “So what if there’s this guy with this magic power, and the only way to beat him is through a very specific process.” And then all the Players decide: who are the characters? What do they do? What do they say? How’s it all work out?
Yeah, pretty much. Collaborative storytelling is the most apt description I’ve heard. Could probably add “rng aided” and you’ve captured pretty much everything about it. It’s definitely one of those “all about the journey, not the destination” sort of things, sort of like a road trip. Also like a road trip, can be anywhere from meticulously planned to basically being railroaded on down to “uh, how about that way?” or anything in between.